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\multicolumn{2}{|c|}{\LARGE\bf THE\hspace*{1cm}STAR\hspace*{1cm}FORMATION\hspace*{1cm}NEWSLETTER} \\ [0.3cm]
\multicolumn{2}{|c|}{\large\em An electronic publication dedicated to early stellar evolution and molecular clouds} \\ [0.3cm]
{\hspace*{0.8cm} No. 126 --- 4 April 2003 } & \multicolumn{1}{r|}{Editor: Bo Reipurth (reipurth@ifa.hawaii.edu)\hspace*{0.8cm}} \\ [-0.1cm]
& \\ \hline
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%\begin{center}
%{\Large\em From the Editor}
%\end{center}
%\vspace*{0.6cm}
\def\v3{\,{\vspace{0.3cm}}}
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\begin{center}
{\Large\em Abstracts of recently accepted papers}
\end{center}
\vspace*{0.6cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Dispersion in the lifetime and accretion rate of T Tauri discs}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Philip J. Armitage$^{1,2}$, Cathie J. Clarke$^3$ and Francesco Palla$^4$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1${JILA, University of Colorado, 440 UCB, Boulder CO 80309-0440, USA} \\
$^2${Department of Astrophysical and Planetary Sciences, University of Colorado,
Boulder CO 80309-0391, USA} \\
$^3${Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK} \\
$^4${Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: pja@jilau1.colorado.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We compare evolutionary models for protoplanetary discs that include
disc winds with observational determinations of the disc lifetime
and accretion rate in Taurus.
Using updated estimates for stellar ages in Taurus,
together with published classifications, we show that the
evolution of the disc fraction with stellar age
is similar to that derived for ensembles of stars within
young clusters. Around 30 percent of stars lose their
discs within 1~Myr, while the remainder have disc lifetimes
that are typically in the 1-10~Myr range. We show that the
latter range of ages is consistent with theoretical
models for disc evolution, provided that there is a dispersion
of around 0.5 in the log of the initial disc mass. The
same range of initial conditions brackets the observed
variation in the accretion rate of Classical T Tauri stars
at a given age. We discuss the expected lifetime of discs in
close binary systems, and show that our models
predict that the disc lifetime is almost constant for
separations exceeding 10~au. This implies a low
predicted fraction of binaries that pair a Classical T Tauri
star with a Weak-lined T Tauri star, and is in better
agreement with observations of the disc lifetime in binaries
than disc models that do not include disc mass loss in a wind.}
% Here you write which journal accepted your paper, for example:
{Accepted by MNRAS}
%% If preprints are available on the WWW you can give the web
%% direction here.
Preprints are available at http://arxiv.org/abs/astro-ph/0303343
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Dynamic cores in hydrostatic disguise}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Javier Ballesteros-Paredes$^{1,2}$, Ralf S.\ Klessen$^{3,4}$ \
and Enrique V\'azquez-Semadeni$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
\def\'#1{\ifx#1i{\accent"13\i}\else{\accent"13#1}\fi}
$^1$ {Department of Astrophysics, American Museum of Natural History.
Central Park West at 79th Street, New York, NY, 10024-5192, U.S.A.} \\
$^2$ {Instituto de Astronom\'ia, UNAM.
Apdo. Postal 72-3 (Xangari),Morelia, Michoac\'an 58089, M\'exico} \\
$^3$ {UCO/Lick Observatory, University of California, Santa Cruz, CA
95064, U.S.A.} \\
$^4$ {Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482
Potsdam, Germany}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: {\tt j.ballesteros@astrosmo.unam.mx}, {\tt
rklessen@aip.de}, {\tt e.vazquez@astrosmo.unam.mx} }
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\def\ximax{{$\xi_{\rm max}$}}
\def\tcero{$t_0$}
\def\tuno{$t_1$}
\def\ssd{SSD}
%% Within the following brackets you place your text:
{We discuss the column density profiles of ``cores'' in
three-dimensional SPH numerical simulations of turbulent molecular
clouds. The SPH scheme allows us to perform a high spatial resolution
analysis of the density maxima (cores) at scales between $\sim$~0.003
and 0.3~pc. We analyze simulations in three different physical
conditions: large scale driving (LSD), small scale driving (SSD), and
random Gaussian initial conditions without driving (GC); each one at
two different timesteps: before self-gravity has become important
(\tcero), and when gravity has been operating such that 5\% of the
total mass in the box has been accretted into cores (\tuno). For this
dataset, we perform Bonnor-Ebert fits to the column density profiles
of cores found by a clump-finding algorithm. We find that, for the
particular fitting procedure we use, 65\%\ of the cores can be matched
to Bonnor-Ebert (BE) profiles, and of these, 47\%\ correspond to {\it
stable} equilibrium configurations with \ximax $< 6.5$, even though
the cores analyzed in the simulations are not in equilibrium, but
instead are dynamically evolving. The temperatures obtained with the
fitting procedure vary between 5 and 60~K (in spite of the simulations
being isothermal, with $T=$ 11.3~K), with the peak of the distribution
being at $T=$ 11~K, and most clumps having fitted temperatures between
5 and 30~K. Central densities obtained with the BE fit tend to be
smaller than the actual central densities of the cores. We also find
that for the LSD and GC cases, there are more BE-like cores at \tcero\
than at \tuno\ with $\xi_{\rm max} \le 20$, while in the case of SSD,
there are more such cores at \tuno\ than at \tcero. We interpret this
as a consequence of the stronger turbulence present in the cores of
run \ssd, which prevents good BE fits in the absence of gravity, and
delays collapse in its presence. Finally, in some cases we find
substantial superposition effects when we analyze the projection of
the density structures, even though the scales over which we project
are small ($\sim 0.18$~pc). As a consequence, different
projections of the same core may give very different values of the BE
fits. Finally, we briefly discuss recent results claiming that Bok
globule B68 is in hydrostatic equilibrium, stressing that they imply
that this core is unstable by a wide margin. We conclude that fitting
BE profiles to observed cores is not an unambiguous test of
hydrostatic equilibrium, and that fit-estimated parameters like mass,
central density, density contrast, temperature, or radial profile of
the BE sphere may differ significantly from the actual values in the
cores.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. }
%% If preprints are available on the WWW you can give the web
%% direction here.
{\tt http://arxiv.org/abs/astro-ph/0304008}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{The $\sigma$ Orionis Substellar population: VLT spectroscopy and
2MASS photometry}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{David Barrado y Navascu\'es$^1$,
V\'\i ctor J.\,S$.$ B\'ejar$^2$,
Reinhard Mundt$^3$,
Eduardo L$.$ Mart\'{\i}n$^4$,
Rafael Rebolo$^{2,5}$,
Mar\'{\i}a Rosa Zapatero Osorio$^1$,
Coryn A.\,L$.$ Bailer-Jones$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1${ Laboratorio de Astrof\'{\i}sica Espacial y F\'{\i}sica Fundamental,
INTA, P.\,O$.$ Box 50727, E--28080 Madrid, Spain}\\
$^2$ {Instituto de Astrof\'\i{}sica de Canarias, E--38205 La Laguna, Tenerife,
Spain}\\
$^3$ {Max-Planck-Institut f\"ur Astronomie, K\"onigstuhl 17, D--69117
Heidelberg, German}\\
$^4$ {Institute of Astronomy. University of Hawaii at Manoa. 2680 Woodlawn
Drive, Honolulu, HI 96822, USA}\\
$^5$ {Consejo Superior de Investigaciones Cient\'{\i}ficas, CSIC, Spain}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: barrado@laeff.esa.es}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{VLT/FORS spectroscopy and 2MASS near-infrared photometry,
together with previously known data, have been used to
establish the membership and the properties of a sample
of low-mass candidate members of the $\sigma$\,Orionis
cluster with masses spanning from 1\,$M_{\odot}$ down to
about 0.013\,$M_{\odot}$ (i.e., deuterium-burning mass
limit). We have observed $K$-band infrared excess and
remarkably intense H$\alpha$ emission in various cluster
members, which, in addition to the previously detected
forbidden emision lines and the presence of Li\,{\sc i}
in absorption at 6708\,\AA, have allowed us to
tentatively classify $\sigma$\,Orionis members as
classical or weak-line T\,Tauri stars and substellar
analogs. Variability of the H$\alpha$ line has been
investigated and detected in some objects. Based on
the $K$-band infrared excesses and the
intensity of H$\alpha$ emission, we estimate that the
minimum disk
frequency of the $\sigma$\,Orionis low-mass population is
in the range 5--12\%.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astronomy \& Astrophysics}
%% If preprints are available on the WWW you can give the web
%% direction here.
Preprint available at http://xxx.lanl.gov/abs/astro-ph/0303462.
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{A Search for Close Binaries in the $\rho$ Ophiuchus Star-Forming
Region}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Mary Barsony$^{1}$, Chris Koresko$^2$ \ and Keith Matthews$^3$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Jet Propulsion Laboratory, MS 169-327, 4800 Oak Grove Drive, Pasadena,
CA 91109 and Space Science Institute, 3100 Marine Street, Suite A353, Boulder, CO
80303-1058, USA} \\
$^2$ {Michelson Science Center, California Institute of Technology,
1201 E. California Blvd., Pasadena, CA 91125, USA} \\
$^3$ {Caltech Optical Observatory, California Institute of Technology,
Pasadena, CA 91125, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: fun@uhuru.jpl.nasa.gov}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We have carried out a new, near-infrared speckle imaging survey
of 19 members of the young stellar population in the nearby (d$=$140 pc),
$\rho$ Ophiuchi cloud core. Results for four binary and one newly discovered
triple system are reported. Data for all known multiple systems among the
pre-main-sequence population of $\rho$ Oph are tabulated. We define a
{\it restricted binary fraction, $F_{b,r}$} and a {\it restricted companion
fraction, $F_{c,r}$}, as counting only those systems most detectable in
the present and previous high-resolution near-infrared imaging surveys,
having separations between 0.1$^{\prime\prime}$ and 1.1$^{\prime\prime}$
and $K$-band magnitude differences, $\Delta K < 3$. Analysis of all the
available multiplicity data results in updated values of $F_{b,r} = 24 \pm 11\%$
and $F_{cr} = 24 \pm 11\%$ for the Ophiuchus pre-main-sequence population.
These values are consistent with the values in the Taurus star-forming region,
and $F_{c,r}$ is in excess by a factor of 2 relative to the Main Sequence
at the 1 $\sigma$ level.
% Here you write which journal accepted your paper, for example:
{ Accepted by Ap. J. (10 July 2003 issue)}
%% If preprints are available on the WWW you can give the web
%% direction here.
Preprint available at http://xxx.lanl.gov/abs/astro-ph/0303595.
\v5
%% Between these brackets you write the title of your paper:
{\large \bf
{[CI] 492\,GHz mapping observations of the high latitude
translucent
cloud \\
MCLD\,123.5+24.9
}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Frank Bensch$^{1,2}$,
Uwe Leuenhagen$^{1,3}$
J\"urgen Stutzki$^{1}$,
Rudolf Schieder$^{1}$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {I.\ Physikalisches Institut der Universit\"at zu K\"oln,
Z\"ulpicher Strasse 77, 50937 K\"oln, Germany} \\
$^2$ {Harvard-Smithsonian Center for Astrophysics, 60 Garden Street,
Cambridge, MA 02138, USA} \\
$^3$ {LB Kiel, Martensdamm 6, 24103 Kiel, Germany}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: fbensch@cfa.harvard.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{
We present the first map of the [CI] $^3$P$_1 \rightarrow$ $^3$P$_0$
fine-structure transition of neutral carbon made towards
a translucent molecular cloud (MCLD\,123.5+24.9, located in the Polaris Flare).
The [CI] observations were made with the Submillimeter
Wave Astronomy Satellite and are supplemented by ground based
observations of $^{12}$CO and $^{13}$CO rotational transitions.
We find that the [CI] emission is spatially extended following the
region bright in $^{12}$CO.
The [CI] to CO line ratios observed throughout the
MCLD\,123.5+24.9 cloud are relatively low, and
the [CI] line flux density is only $\sim50$\% of the emission by the
three lowest CO rotational transitions. However, the ratios are still
within the range observed along selected lines of sight towards
other diffuse and translucent molecular clouds.
Assuming LTE conditions for the neutral atomic
carbon with an excitation
temperature of 8\,K derived from the $^{12}$CO spectra, we derive a
total carbon column density of ($0.25-1)\times 10^{17}$\,cm$^{-2}$
and a C to CO column density ratio between 0.2 and 1.1.
Comparison with a PDR (photo-dominated region) model
shows that the model
consistently would require uncomfortably high values for the
gas volume density in order to reproduce the low [CI] to CO line ratios
observed ($n>10^5$\,cm$^{-3}$), unless we assume that the line emitting
clumps are embedded in an interclump medium with a density of
$n<10^3$\,cm$^{-3}$. The low density interclump medium does not significantly
contribute to the observed [CI] and CO line emission, but the molecular
hydrogen in the gas provides an effective shielding for the CO in the
embedded clumps by blocking the FUV photons at the frequencies
of CO line transition to the pre-dissociation states. This
reduces the photodissociation of CO and thus the abundance of neutral
and ionized carbon in the denser clumps.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by The Astrophysical Journal}
%% If preprints are available on the WWW you can give the web
%% direction here.
cfa-www.harvard.edu/sfgroup/papers/fbensch-mar03.ps
%\end{document}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{On the Radii of Extrasolar Giant Planets}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Peter Bodenheimer, Gregory Laughlin, \ and Douglas N. C. Lin }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USA}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: laughlin@ucolick.org}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{
We have computed evolutionary models for extrasolar planets which range
in mass from 0.1 $M_{\rm JUP}$ to 3.0 $M_{\rm JUP}$, and which range in
equilibrium temperature from 113 K to 2000 K. We present four
sequences of models, designed to show the structural
effects of a solid (20 $M_{\oplus}$)
core and of internal heating due to the conversion of kinetic to thermal
energy at pressures of tens of bars. The model radii at ages of 4--5 Gyr
are intended for future
comparisons with radii derived from observations of
transiting extrasolar planets. To provide such comparisons, we expect
that of order 10 transiting planets with orbital periods less than 200 days
can be detected
around bright ($V<10-11$) main-sequence stars for which accurate
well-sampled radial velocity (RV) measurements can also be readily accumulated.
Through these observations, structural properties of the planets will be
derivable, particularly for low-mass, high-temperature planets.
Implications regarding the transiting companion to OGLE-TR-56
recently announced by Konacki et al. are discussed.
With regard to the transiting planet, HD 209458b, we find,
in accordance with other recent calculations,
that models without internal heating predict a radius
that is $\sim 0.3 R_{\rm JUP}$ smaller than the observed radius.
Two resolutions have been proposed for this discrepancy.
Guillot \& Showman hypothesize that deposition of kinetic wind energy at
pressures of tens of bars is responsible for heating the planet and maintaining
its large size. Our models confirm that dissipation of the type proposed
by Guillot \& Showman can indeed produce a large radius for HD 209458b.
Bodenheimer, Lin \& Mardling suggest that HD 209458b
owes its large size to dissipation of energy arising from
ongoing tidal circularization
of the planetary orbit. This mechanism requires the presence of an
additional planetary companion to continuously force the eccentricity.
We show that residual scatter
in the current RV data set for HD 209458b is consistent with
the presence of an as-of-yet undetected second companion, and that
further RV monitoring of HD 209458 is indicated.
Tidal circularization theory also can provide constraints on planetary radii.
Extrasolar giant planets
with periods of order 7 days should be actively circularizing. We find that
the observed eccentricities
of $e \sim 0.14$ for both HD 217107b ($P=6.276~{\rm d}$; $M\sin i =1.80~M_{\rm
JUP}$),
and for HD 68988b ($P=7.125~{\rm d}$, $M\sin i =1.29~M_{\rm JUP}$) likely
indicate either relatively small planetary radii for these objects
($ R \sim 1.1~R_{\rm JUP}$) or tidal quality factors
in the neighborhood of $Q_{\rm P} \sim 10^{7}$. For these two
planets, it will be difficult to differentiate the contribution
from tidal and kinetic heating. But the radius of
HD 168746b ($P=6.403~{\rm d}$, $M\sin i =0.23~M_{\rm JUP}$) is sensitive
to whether the planet's interior is heated by tidal dissipation or
kinetic heating. The tidal circularization time scale of this
planet is shorter than the age of its host star, but we show that within
the observational uncertainties, the published RV data can also
be fit with a circular orbit for this planet.
As more RV planets with periods of
order a week are discovered, $Q_{\rm P} (T_{\rm eq},M_{\rm P})$ and
$R_{\rm P}(T_{\rm eq},M_{\rm P})$
will become better determined.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by the Astrophys. J. }
%% If preprints are available on the WWW you can give the web
%% direction here.
http://xxx.lanl.gov/abs/astro-ph/0303541
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Abundant gas-phase H$_2$O in absorption toward massive
protostars}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ A.M.S. Boonman$^1$ \ and E.F. van Dishoeck$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Sterrewacht Leiden, P.O. Box 9513, 2300 RA
Leiden, The Netherlands}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: boonman@strw.leidenuniv.nl}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\def\gtsim{{_>\atop{^\sim}}}
%% Within the following brackets you place your text:
{We present infrared spectra of gas-phase H$_2$O around 6~$\mu$m toward
12 deeply embedded massive
protostars obtained with the Short Wavelength Spectrometer on board the
Infrared Space Observatory (ISO). The $\nu_2$ ro-vibrational band has been
detected toward 7 of the sources and the excitation temperatures indicate
an origin in the warm gas at $T_{\mathrm{ex}}\gtsim$250~K.
Typical derived gas-phase H$_2$O abundances are
$\sim$5$\times$10$^{-6}$--6$\times$10$^{-5}$, with the abundances
increasing with the temperature of the warm gas. The inferred gas/solid
ratios show a similar trend with temperature and suggest that
grain-mantle evaporation is important. The increasing gas/solid ratio
correlates with other indicators of
increased temperatures. If the higher temperatures are due to
a larger ratio of source luminosity to envelope mass,
this makes gas-phase H$_2$O a good
evolutionary tracer. Comparison with
chemical models shows that three different chemical processes,
ice evaporation, high-$T$ chemistry, and shocks, can reproduce the high
inferred gas-phase H$_2$O abundances.
In a forthcoming paper each of these processes are investigated
in more detail in comparison with data from the Long Wavelength
Spectrometer
on board ISO and the Submillimeter Wave Astronomy Satellite (SWAS).
Comparison with existing SWAS data indicates that a jump in the H$_2$O
abundance is present and that the observed $\nu_2$ ro-vibrational band
traces primarily the warm inner envelope.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by A\&A }
%% If preprints are available on the WWW you can give the web
%% direction here.
http://www.strw.leidenuniv.nl/$\sim$boonman/papers/h2osws.pdf
\v5
{\large\bf{Theory of Twisted Trunks}}
{\bf{ P. Carlqvist$^1$, G.F. Gahm $^2$ \ and H. Kristen $^3$ }}
$^1$ {Alfv\'en Laboratory, Royal Institute of Technology, SE-100 44
Stockholm, Sweden} \\
$^2$ {SCFAB, Stockholm Observatory, SE-106 91 Stockholm, Sweden} \\
$^3$ {Precise Biometrics, Dag Hammarskj\"olds v\"ag 2, SE-224 64 Lund,
Sweden}
{E-mail contact: gahm@astro.su.se}
{Using the 2.6 m Nordic Optical Telescope we have observed a large number of
elephant trunks in several H II regions. Here, we present a small selection
of this material consisting of a few large, well-developed trunks, and some
smaller ones. We find that: (i) the well-developed trunks are made up of
dark filaments and knots which show evidence of twisted structures, (ii)
the trunks are connected with essentially two filamentary legs running in
V-shape, and (iii) all trunks have the maximum extinction in their heads.
We advance a theory of twisted elephant trunks which is based on the
presence of magnetic flux ropes in molecular clouds where hot OB stars are
formed. If the rope contains a local condensation it may adopt a V-shape as
the HII region around the hot stars expands. If, in addition, the
magnetic field in the rope is sufficiently twisted, the rope may form a
double helix at the apex of the V. The double helix is identified with the
twisted elephant trunks.
In order to illustrate the mechanisms behind the double helix we have
constructed a mechanical analogy model of the magnetic flux rope in which
the rope has been replaced by a bundle of elastic strings loaded by a
weight. Experiments with the model clearly show that part of the bundle
will transform into a double helix when the twist of the bundle is
sufficiently large. We have also worked out a simple theoretical model of a
mass-loaded magnetic flux rope. Numerical calculations show that a double
helix will indeed form when the twist of the rope exceeds a certain
critical limit. Numerical model calculations are applied to both the
analogy model experiments and one of the well-developed elephant trunks. On
the basis of our model we also suggest a new interpretation of the so
called EGGs.
The double helix mechanism is
quite general, and should be active also in other suitable
environments. One such environment may be the shell of supernova remnants.
Another example is the expanding bubble outlined by the North Celestial
Pole Loop}
{ Accepted by A\&A }
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Adaptive optics imaging survey of the Tucana-Horologium
association}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
%%{\bf{ First Author$^1$, Second Author$^2$ \ and Third Author$^3$ }}
{\bf{G. Chauvin$^1$,
M. Thomson$^{1,2}$,
C. Dumas$^3$,
J-L. Beuzit$^1$,
P. Lowrance$^3$,
T. Fusco$^4$,
A-M. Lagrange$^1$,
B. Zuckerman$^5$
\ and
D. Mouillet$^6$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
%$^1$ {European Southern Observatory, Casilla 19001, Santiago 19,
%$^2$ {Cerro Tololo Inter-American Observatory, National Optical
% Observatories, Casilla 603, La Serena, Chile} \\
%$^3$ {Las Campanas Observatory, Carnegie Inst. of Washington, Casilla
% 601, La Serena, Chile}
$^1${Laboratoire d'Astrophysique, Observatoire de
Grenoble, 414, Rue de la piscine, Saint-Martin
d'H\`eres, France}\\
$^2${Imperial College of Science, Technology and
Medecine, Exhibition Road, London SW7 2AZ, England}\\
$^3${Jet Propulsion Laboratory, Mail Stop 183-501,
California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA
91109, USA\\
$^4${ONERA, BP52 29 Avenue de la Dividion Leclerc
Ch\^atillon Cedex, France}\\
$^5${Department of Physics and Astronomy, University of
California, Los Angeles, 8371 Math Science Building, Box 951562, CA
90095-1562, USA}\\
$^6${Laboratoire d'Astrophysique, Observatoire
Midi-Pyr\'en\'enes, Tarbes, France}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for
{E-mail contact: Gael.Chauvin@obs.ujf-grenoble.fr}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We present the results of an adaptive optics (AO) imaging survey of
the common associations of Tucana and Horologium, carried out at the
ESO 3.6m telescope with the ADONIS/SHARPII system. Based on our
observations of two dozen probable association members, HIP~1910 and
HIP~108422 appear to have low-mass stellar companions, while HIP~6856
and GSC~8047-0232 have possible sub-stellar candidate companions.
Astrometric measurements, performed in November 2000 and October 2001,
indicate that HIP~1910 B likely is bound to its primary, but are
inconclusive in the case of the candidate companion to HIP~6856.
Additional observations are needed to confirm the HIP~6856
companionship as well as for HIP~108422 and GSC~8047-0232.}
% Here you write which journal accepted your paper, for example:
{ Accepted by A\&A}
%% If preprints are available on the WWW you can give the web
%% direction here.
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{The mass-velocity and intensity-velocity relations in
jet-driven molecular outflows}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Turlough P.\ Downes$^1$ and Sylvie Cabrit$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {School of Mathematical Sciences, Dublin City University,
Glasnevin, Dublin 9, Ireland} \\
$^2$ {LERMA, Observatoire de Paris, 61 Av.\ de l'Observatoire, F-75014
Paris, France}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: turlough.downes@dcu.ie}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We use numerical simulations to examine the mass-velocity and
intensity-velocity relations in the CO J=2-1 and H$_2$ S(1)1-0 lines for
jet-driven molecular outflows. Contrary to previous expectations, we
find that the mass-velocity relation for the swept-up gas is a single
power-law, with a shallow slope $\simeq -1.5$ and no break to a steeper
slope at high velocities. An analytic bowshock model with no post-shock
mixing is shown to reproduce this behaviour very well.
We show that molecular dissociation and the temperature dependence of
the line emissivity are both critical in defining the shape of the line
profiles at velocities above $\sim$ 20 km s$^{-1}$. In particular, the
simulated CO J=2-1 intensity-velocity relation does show a break in
slope, even
though the underlying mass distribution does not. These predicted CO
profiles are found to compare remarkably well with observations of
molecular outflows, both in terms of the slopes at low and high
velocities and in terms of the range of break velocities at which the
change in slope occurs. Shallower slopes are predicted at high velocity
in higher excitation lines, such as H$_2$ S(1)1-0.
This work indicates that, in jet-driven outflows, the CO J=2-1 intensity
profile reflects the slope of the underlying mass-velocity distribution
only at velocities $\le $ 20 km/s, and that higher temperature tracers
are required to probe the mass distribution at higher speed.}
% Here you write which journal accepted your paper, for example:
{Accepted by Astronomy and Astrophysics}
%% If preprints are available on the WWW you can give the web
%% direction here.
{Preprints available from
http://www.dcu.ie/\char126downest/documents/papers/outflows.ps.gz}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{No Fossil Disk in the T Tauri Multiple System V773 Tau}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Gaspard Duch\^ene$^1$, Andrea M. Ghez$^1$, Caer McCabe$^1$
\ and Alycia J. Weinberger$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Division of Astronomy and Astrophysics, UCLA, Los Angeles, CA
90095-1562, USA} \\
$^2$ {Department of Terrestrial Magnetism, Carnegie
Institution of Washington, Washington, DC 20015, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: duchene@astro.ucla.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\newcommand{\vt}{V\,773\,Tau}
\newcommand{\vc}{V\,773\,Tau\,C}
\newcommand{\vd}{V\,773\,Tau\,D}
\newcommand{\brg}{Br$\gamma$}
%% Within the following brackets you place your text:
{ We present new multi-epoch near-infrared and optical
high-angular images of the {\vt} pre-main sequence triple
system, a weak-line T\,Tauri (WTTS) system in which the
presence of an evolved, ``fossil'' protoplanetary disk has
been inferred on the basis of a significant infrared
excess. Our images reveal a fourth object bound to the
system, {\vd}. While it is much fainter than all other
components at 2\,$\mu$m, it is the brightest source in the
system at 4.7\,$\mu$m. We also present medium-resolution $K$
band adaptive optics spectroscopy of this object, which is
featureless with the exception of a weak {\brg} emission
line. Based on this spectrum and on the spectral energy
distribution of the system, we show that {\vd} is
another member of the small class of ``infrared companions''
(IRCs) to T\,Tauri stars (TTS). It is the least luminous,
and probably the least massive, component of the system, as
opposed to most other IRCs, which suggests that numerous
low-luminosity IRCs such as {\vd} may still remain to be
discovered. Furthermore, it is the source of the strong IR
excess in the system. We therefore reject the interpretation
of this excess as the signature of a fossil (or ``passive'')
disk and further suggest that these systems may be much less
frequent than previously thought.
We further show that {\vc} is a variable classical TTS
(CTTS) and that its motion provides a well constrained
orbital model. We show that {\vd} can be dynamically stable
within this quadruple system if its orbit is highly
inclined. Finally, {\vt} is the first multiple system to
display such a variety of evolutionary states (WTTS, CTTS,
IRC), which may be the consequence of the strong star-star
interactions in this compact quadruple system.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astroph. J. }
%% If preprints are available on the WWW you can give the web
%% direction here.
Preprint available at http://xxx.lanl.gov/abs/astro-ph/0303648
\v5
\newcommand{\etal}{et al.}
\newcommand{\msun}{{\,\rm M}_{\odot}}
\newcommand{\tco}{\ifmmode {^{13}{\rm CO}} \else {$^{13}{\rm CO}$}\fi}
\newcommand{\dco}{\ifmmode {^{12}{\rm CO}} \else {$^{12}{\rm CO}$}\fi}
\newcommand{\juz}{\ifmmode {{\rm J}=1\rightarrow\0} \else
{J=1$\rightarrow$0}\fi}
\newcommand{\jdu}{\ifmmode {{\rm J}=2\rightarrow\1} \else {J=2$\rightarrow$1}\fi}
%
%% Between these brackets you write the title of your paper:
{\large\bf{The BP Tau disk: a missing link between Class II and
III objects?}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ A.Dutrey$^1$, S.Guilloteau$^2$ and M.Simon$^3$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ Laboratoire d'Astrophysique de l'Observatoire de
Grenoble, BP 53, F-38041 Grenoble Cedex 9, France \\
$^2$ Institut de Radio Astronomie Millim\'etrique, 300 Rue de la
Piscine, F-38406 Saint Martin d'H\`eres, France \\
$^3$ Dept. of Physics and Astronomy, State Univ. of New York,
Stony Brook, NY 11794-3800, U.S.A.
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: Anne.Dutrey@obs.ujf-grenoble.fr}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%
%% Within the following brackets you place your text:
{We present new single-dish (30-m) observations and an improved
analysis of our earlier interferometric observations (Simon \etal\
2000) of BP Tau. Our analysis yields a detailed description of the
properties of the circumstellar disk. The disk is small (outer
radius 120 AU) and marginally optically thick in the \dco~\jdu\
line. It is also relatively hot, about 50~K at 100~AU. The mm
continuum emission is consistent with a thermal emission from
circumstellar dust with an emissivity index $\beta \simeq 0.7$,
and a disk mass about $1.2\,10^{-3} \msun$. The anomalously low
\dco\ to dust emission ratio implies that either CO is depleted by
a factor of order 150 with respect to H$_2$, or a very low gas to
dust ratio, or highly anomalous dust properties. The disk exhibits
direct evidence for Keplerian rotation, but because of a
combination of insufficient resolution and optically thin CO
emission, the mass derived for the star remains inaccurate
(between 0.6 and $1.3 \msun$ for 140 pc). The unusual properties
of the circumstellar disk suggest that BP Tau may be a transient
object in the process of clearing its disk.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron.Astrophys.}
%% If preprints are available on the WWW you can give the web
%% direction here.
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{The influence of grains on the propagation and structure
of C-type shock waves in interstellar molecular clouds}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ D. R. Flower$^1$ \ and G. Pineau des For\^ets$^{2,3}$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Physics Department, The University, Durham DH1 3LE, UK} \\
$^2$ {IAS, Universit\'e de Paris-Sud, 91405 Orsay, France} \\
$^3$ {LUTH, Observatoire de Paris, 92195 Meudon Cedex, France}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for
{E-mail contact: david.flower@dur.ac.uk}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{Gas-grain interactions can have important consequences for the physics
and chemistry of shock waves propagating in molecular clouds. The grains
can be both a source and a sink of molecules, and their inertia can
modify the dynamics of the propagation of, in particular, C-type
shock waves. The degree of charging of the grains, both in the
preshock gas and in the shock wave itself, is a significant parameter.
The population of interstellar grains extends from large molecules,
which we represent by polycyclic aromatic hydrocarbons, to much
larger particles, composed of silicates and amorphous carbon material.
The influence of the inertia of the grains on the dynamics of the
flow is modelled in detail. We find that collisions between charged
and neutral grains, driven by ion-neutral drift in C-type shock waves,
may lead to the shattering of a large fraction of the amorphous
carbon material.}
% Here you write which journal accepted your paper, for example:
{ Accepted by MNRAS }
%% If preprints are available on the WWW you can give the web
%% direction here.
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{The role of ambipolar diffusion in the fragmentation
of condensations of the primordial gas}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ D. R. Flower$^1$ \ and G. Pineau des For\^ets$^{2,3}$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Physics Department, The University, Durham DH1 3LE, UK} \\
$^2$ {IAS, Universit\'e de Paris-Sud, 91405 Orsay, France} \\
$^3$ {LUTH, Observatoire de Paris, 92195 Meudon Cedex, France}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for
{E-mail contact: david.flower@dur.ac.uk}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We consider the evolution and fragmentation of cylindrical filaments
of the primordial gas. The filaments are formed following shock
compression and heating, occurring subsequent to the gravitational
collapse of condensations of the primordial medium. The role of
ambipolar diffusion is studied, under circumstances where the
magnetic energy density is comparable with the thermal energy
density in the filaments, prior to their collapse. It is shown
that ambipolar diffusion reduces the masses of the fragments by
about an order of magnitude when the fractional ionization of
the gas n(H$^+$)/n(H) is of the order of 10$^{-8}$ or less.
Under these conditions, ambipolar diffusion is sufficiently
rapid for the fragment masses to be similar to those computed
neglecting the magnetic field. Attention is drawn to the importance
of the H$^+$ (H$_2$, h$\nu$) H$^+_3$ reaction, whose rate
coefficient is very uncertain.}
% Here you write which journal accepted your paper, for example:
{ Accepted by MNRAS }
%% If preprints are available on the WWW you can give the web
%% direction here.
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{The Orion nebula (M42) Herbig-Haro object, HH~201,
within the tip of a molecular finger}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ M. F. Graham$^{1}$, J. Meaburn$^{1}$ and M. P. Redman$^{2}$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^{1}$ {Jodrell Bank Observatory, Department of Physics \& Astronomy,
University of Manchester, Macclesfield, Cheshire SK11 9DL, UK} \\
$^{2}${Department of Physics and Astronomy, University College London,
Gower Street, London WC1E 6BT, UK}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: mgraham@ast.man.ac.uk}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\newcommand{\sii}{[S~{\sc ii}]~6716 \& 6731~\AA}
\newcommand{\htwo}{H$_2$}
\newcommand{\htwoa}{H$_2~v=1-0$~S(1)}
\def\hst{\textit{HST}}
\def\kms{\ifmmode{{\rm km\,s}^{-1}}\else{km~s$^{-1}$}\fi}
%% Within the following brackets you place your text:
{The most prominent Herbig-Haro (HH) object, HH~201, in the Orion
nebula is investigated using optical spectroscopy along with optical
and infrared images. An infrared Subaru \htwoa\ image of the region
surrounding HH~201's optical line emission has yielded the discovery
of a faint \htwo\ finger associated with HH~201. The \htwo\ finger
is seen to share a common width and orientation with the optical
line emission. Therefore, it is unlikely that the association is
caused by a chance superposition along the line of sight. The finger
is found to precede the optical line emission, which is inconsistent
with this \htwo\ emission being produced within a bowshock. The origin
of this finger is discussed in the context of the current
understanding of HH objects and the Orion molecular fingers.
Multi-epoch \hst\ \sii\ images are used to
measure the proper motions of the various knots present in the
filamentary structure of HH~201. Tangential velocities of between
40~\kms\ and 178~\kms\ are found. Two new knots with associated proper
motions are found in the wake of HH~201 and the general structure of
the tangential flow is shown by means of a multi-epoch difference
image.
\sii\ spectra taken with the RGO spectrograph are used to
spectroscopically resolve the velocity profile of HH~201 into distinct
components with radial velocities of between -267~\kms\ and
-9~\kms. Using the \sii\ line ratios, the local electron density of gas
at the various velocities is found to be between 830~cm$^{-3}$ and
12200~cm$^{-3}$. Combining radial and tangential velocities, the
angle between the direction of motion and the line of sight is found
to be approximately 30$^{\circ}$. Assuming that the emission knots
and velocity components correspond to condensations in a bowshock, a
shock velocity at the head of HH~201 of 295~\kms\ is
established. Using this combination of optical and infrared data, the
morphology and kinematics of HH~201 and its immediate environs are
elucidated.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Monthly Notices of the Royal Astronomical Society }
%% If preprints are available on the WWW you can give the web
%% direction here.
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Evidence for a T Tauri Phase in Young Brown Dwarfs}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Ray Jayawardhana$^1$, Subhanjoy Mohanty$^2$ \ and Gibor Basri$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Astronomy, University of Michigan, 830 Dennison
Building, Ann Arbor, MI 48109, USA}\\
$^2$ {Harvard-Smithsonian Center for Astrophysics, 60 Garden St.,
Cambridge, MA 02138, USA}\\
$^3$ {Department of Astronomy, University of California, 601 Campbell
Hall, Berkeley, CA 94720, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: rayjay@umich.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{As part of a multi-faceted program to investigate the origin and early
evolution of sub-stellar objects, we present high-resolution Keck optical
spectra of 14 very low mass sources in the IC 348 young cluster and the
Taurus star-forming cloud. All of our targets, which span a range of
spectral types from M5 to M8, exhibit moderate to very strong H$\alpha$
emission. In half of the IC 348 objects, the H$\alpha$ profiles are broad
and asymmetric, indicative of on-going accretion. Of these, IC348-355 (M8)
is the lowest mass object to date to show accretion-like H$\alpha$.
Three of our $\sim$ M6 IC 348 targets with broad H$\alpha$ also harbor
broad OI (8446\AA) and CaII (8662\AA) emission, and one
shows broad HeI (6678\AA) emission; these features are usually seen in
strongly accreting classical T Tauri stars. We find that in very low mass
accretors, the H$\alpha$ profile may be somewhat narrower than that in
higher
mass stars. We propose that low accretion rates combined with small infall
velocities at very low masses can conspire to produce this effect. In the
non-accretors in our sample, H$\alpha$ emission is commensurate with, or
higher than, saturated levels in field M dwarfs of similar spectral
type. Our results constitute the most compelling evidence to date that
young brown dwarfs undergo a T Tauri-like accretion phase similar to that
in stars. This is consistent with a common origin for most low-mass stars,
brown dwarfs and isolated planetary mass objects.}
% Here you write which journal accepted your paper, for example:
{ Accepted by The Astrophysical Journal }
%% If preprints are available on the WWW you can give the web
%% direction here.
Available at http://arxiv.org/abs/astro-ph/0303565
\v5
{\large\bf{
The G11.11-0.12 Infrared-Dark Cloud:\\
Anomalous Dust and a Non-Magnetic Isothermal Model
}}
{\bf{
Doug Johnstone$^{1}$, Jason D. Fiege$^{1}$,
R.O.\ Redman$^{1}$, P.A.\ Feldman$^{1}$, and Sean J. Carey$^{2}$
}}
$^1$ {NRC Canada, Herzberg Institute of Astrophysics,
5071 West Saanich Rd, Victoria, BC, V9E 2E7, Canada}
\\
$^2$ {SIRTF Science Center, California Institute of Technology,
Mail Code 220-6, Pasadena, CA 91125, USA}
{E-mail contact: doug.johnstone@nrc-crnc.gc.ca}
{
The G11.11-0.12 Infrared-Dark Cloud has a filamentary
appearance, both in absorption against the diffuse 8$\mu$m
Galactic background, and in emission from cold dust at
850$\mu$m. Detailed comparison of the dust properties at
these two wavelengths reveals that standard models for the
diffuse interstellar dust in the Galaxy are not consistent
with the observations. The ratio of absorption coefficients
within the cloud is $\kappa_8/\kappa_{850} \le 1010$, which
is well below that expected for the diffuse ISM where
$\kappa_8/\kappa_{850} \sim 1700$. This may be due to the
formation of ice mantles on the dust and grain coagulation,
both of which are expected within dense regions of molecular
clouds. The 850$\mu$m emission probes the underlying radial
structure of the filament. The profile is well represented
by a marginally resolved central region and a steeply
falling envelope, with $\Sigma(r) \propto r^{-\alpha}$,
where $\alpha \geq 3$, indicating that G11.11-0.12 is the
first observed filament with a profile similar to that of a
non-magnetic isothermal cylinder.
}
{Accepted by Ap.J. Letters }
astro-ph 303651
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{The Physical and Chemical Status of Pre-protostellar Core B68}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Shih-Ping Lai$^1$, Thangasamy Velusamy$^1$, Williams Langer$^1$, Tom
Kuiper$^1$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Jet Propulsion Laboratory, California Institute of Technology}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: slai@jpl.nasa.gov}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\def\c3h2{C$_3$H$_2$}
\def\nh3{NH$_3$}
\def\n2h+{N$_2$H$^+$}
%% Within the following brackets you place your text:
{We have investigated the physical and chemical status of
the pre-protostellar core B68. A previous extinction study suggested that
the density profile of B68 is remarkably consistent with
a Bonnor-Ebert sphere with 2.1 $M_{\odot}$ at 16 K.
We mapped B68 in \c3h2, CCS, and \nh3 with
the Deep Space Network (DSN) 70m telescope at Goldstone.
Our results show that the \nh3 peak coincides with the dust continuum peak,
whereas CCS and \c3h2 are offset from the \nh3 and dust peaks.
The B68 chemical structure is consistent with that seen in other such
pre-protostellar cores (L1498, L1544) and is explained by time dependent
chemical models that include depletion.
We measured the kinetic temperature of B68 with \nh3 (1,1) and
(2,2) spectra obtained with a DSN 34m telescope.
We find that the kinetic temperature of B68 is
only 11 K which is significantly lower than that previously assumed.
We also derive the non-thermal linewidth in B68,
and show that B68 is thermally dominated with little contribution from
turbulence support ($ $}\kern -0.8 em \lower 0.7
ex\hbox{$\sim$}\,}
%% Within the following brackets you place your text:
{In the
framework of a multi-wavelengths study of NGC\,3603 we have performed
near and mid infrared imaging to investigate the nature and the
evolutionary status of the highly reddened sources NGC\,3603
IRS\,9A--C. These sources are located on the OB cluster facing side
of the massive molecular cloud core NGC\,3603 MM\,2 and were
apparently only recently revealed from most of their natal environment
by strong stellar winds and energetic radiation originating from the
nearby high mass cluster stars. \\ On the basis of the steeply rising
spectral energy distributions and the large near and mid infrared
excess emission we conclude that IRS\,9A--C represent (the brightest
members of) a sparse association of high mass protostars, solely
embedded in the gravitationally bound material of their circumstellar
envelopes but largely blown free from gas\,$+$\,dust of the pristine
molecular cloud core. \\ Fitting blackbody functions to the overall
spectral energy distribution at near and mid infrared wavelengths we
identify two dust components at temperatures of 250\,K and 1150\,K for
IRS\,9A and 250\,K and 700-750\,K for IRS\,9B\,/\,9C. From the mid
infrared fluxes we deduce lower limits for the gas\,$+$\,dust masses
of the circumstellar envelopes: $\gtsimeq$\,0.1\,$\cal M_{\odot}$ for
IRS\,9A and $\gtsimeq$\,3\,$\cdot$\,10$^{-3}$\,$\cal M_{\odot}$ for
IRS\,9B\,/\,9C. Estimates of the total luminosities are on the order
of 10$^{5}$\,$L_{\odot}$ and 10$^{3}$\,$L_{\odot}$ for IRS\,9A and
IRS\,9B\,/\,9C, respectively. \\ Finally, our interpretation of
IRS\,9A--C being protostars is supported by recent ATCA data. The
measured 3\,cm and 6\,cm radio fluxes of IRS\,9A can neither be
explained by non-thermal emission nor by thermal dust emission. From
the spectral index $\alpha_{\rm radio}$\,$\sim$\,0.3 we conclude that
the observed radio emission is thermal bremsstrahlung and most likely
excited externally by ionizing photons originating from the nearby OB
cluster. }
% Here you write which journal accepted your paper, for example:
{Accepted by A\&A}
%% If preprints are available on the WWW you can give the web
%% direction here.
\v5
%% Between these brackets you write the title of your paper:
{\large \bf{The lithium depletion boundary and the age of
NGC 2547}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{J.M. Oliveira$^{1}$, R.D. Jeffries$^{1}$, C.R. Devey$^{1}$, D. Barrado y
Navascu\'{e}s$^{2}$, T. Naylor$^{3}$, J.R. Stauffer$^{4}$ and E.J. Totten$^{1}$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^{1}${School of Chemistry \& Physics, Keele University, Keele, Staffordshire, ST5 5BG,
UK}\\
$^{2}$ {LAEFF-INTA, P.O. Box 50727, E-28080 Madrid, Spain}\\
$^{3}$ {School of Physics, University of Exeter, Stocker Road, Exeter,
EX4 4QL, UK}\\
$^{4}$ {SIRTF Science Center, California Institute of Technology, MS
314-6, {Pasadena, CA 91125, USA}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: joana@astro.keele.ac.uk}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We present the results of a photometric and spectroscopic survey of
cool M dwarf candidates in the young open cluster NGC\,2547. Using the
2dF fiber spectrograph, we have searched for the luminosity at which
lithium remains unburned in an attempt to constrain the cluster age.
The lack of a population of individual lithium-rich objects towards the faint
end of our sample places a very strong lower limit to the cluster age of
35\,Myr. However, the detection of lithium in the averaged spectra of our
faintest targets suggests that the lithium depletion boundary lies at
$9.5
1.9$~\micron, but {\it not}~$\gg 4$~\micron.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by ApJ Letters (Issue 20 April 2003) }
%% If preprints are available on the WWW you can give the web
%% direction here.
Preprints --- {\tt
http://www.astro.ucla.edu/$\sim$shuping/research/OrionProplyds}
\v5
{\large\bf{Numerous Proplyd Candidates in the Harsh Environment of the
Carina Nebula}}
{\bf{ Nathan Smith$^1$, John Bally$^1$, and Jon A.\ Morse$^1$ }}
$^1$ {Center for Astrophysics and Space Astronomy, University of
Colorado, 389 UCB, Boulder, CO 80309, USA}
{E-mail contact: nathans@casa.colorado.edu}
{
We report the discovery of dozens of compact objects in the Carina
Nebula (NGC~3372) that closely resemble proplyds (photoablating
proto-planetary disks and dark silhouette disks) seen previously in
the Orion Nebula. This is the first detection of a large number of
such objects outside Orion. They imply that low- and
intermediate-mass star formation is proceeding actively in Carina,
despite threatening conditions imposed by very hot massive stars. The
proplyd candidates that we have detected are larger than those in
Orion, but more compact than irregular molecular globules within the
H II region. Smaller proplyds may still be lurking in Carina,
waiting to be discovered. Orion apparently lacks objects of
comparable size, and we consider several explanations. Larger
proplyds may come from larger and more massive circumstellar disks
surrounding young Herbig Ae/Be stars that should be numerous in
Carina. Alternatively, far-UV radiation from the massive star $\eta$
Carinae may have, in the recent past, enhanced photoablation and
expanded proplyd ionization fronts. Some unusual proplyd candidates
may also imply that time-dependent effects associated with $\eta$
Car's current evolutionary state may be critical.
}
{Accepted by Astrophysical Journal, Letters}
\v5
{\large\bf{Multi-wavelength spectroscopy of the bipolar outflow from
Cepheus\,E}}
{\bf{ Michael D. Smith$^1$, Dirk Froebrich$^2$ \ and Jochen Eisl\"offel$^2$ }}
$^1$ {Armagh Observatory, College Hill, Armagh BT61 9DG,Northern Ireland} \\
$^2$ {Th\"uringer Landessternwarte Tautenburg, Sternwarte 5,
D-07778 Tautenburg, Germany}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: mds@star.arm.ac.uk, frobrich@tls-tautenburg.de,
jochen@tls-tautenburg.de }
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{Cepheus\,E is the site of an exceptional example of a protostellar
outflow with a very young dynamical age and extremely high near
infrared luminosity. We combine molecular spectroscopic data from
the submillimeter to the near infrared in order to interpret the
rotational excitation of CO and the ro-vibrational excitation of
H$_2$. We conclude that C-type shocks with a paraboloidal bow shock
geometry can simultaneously explain all the molecular excitations.
Extinction accounts for the deviation of the column densities from
local thermodynamic equilibrium. A difference in the extinction
between the red and blue-shifted outflow lobes may account for the
measured flux difference. The outflow is deeply embedded in a
clump of density 10$^5$\,cm$^{-3}$, yet a good fraction of atomic
hydrogen, about 40\%, is required to explain the excitation and
statistical equilibrium. We propose that this atomic component arises,
self-consistently, from the dissociated gas at the apex of the leading
bow shocks and the relatively long molecule reformation time. At least
20 bow shocks are required in each lobe, although these may be
sub-divided into smaller bows and turbulent shocked regions. The
total outflow mechanical power and cooling amounts to over
30\,L$_{\odot}$, almost half the source's bolometric luminosity.
Nevertheless, only about 6\% of the clump mass has been set in
outward motion by the outflow, allowing a collapse to continue.}
{ Accepted by Astrophys. J. }
%% If preprints are available on the WWW you can give the web
%% direction here.
Preprints available at http://www.tls-tautenburg.de/research/research.html
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Interaction between the Outflow and the Core in IRAM 04191+1522}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Shigehisa Takakuwa$^1$$^2$, Nagayoshi Ohashi$^1$, \ and
Naomi Hirano$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Academia Sinica Institute of Astronomy and Astrophysics,
P.O. Box 23-141, Taipei 106, Taiwan} \\
$^2$ {Present address: Harvard-Smithsonian Center for Astrophysics,
82 Pu'uhonu Place, Suite 210, Hilo, HI 96720, U.S.A.}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: stakakuwa@sma.hawaii.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We have carried out mapping observations of the
molecular core associated with the young Class 0 protostar, IRAM
04191+1522, in the CH$_{\rm 3}$OH
($J_{\rm K}$=2$_{\rm K}$--1$_{\rm K}$) and C$^{\rm 34}$S ($J$=2--1) lines
using the 45 m telescope at Nobeyama Radio Observatory.
Our observations have revealed that
there is a condensation associated with the protostar, elongated
in the east-west direction mostly perpendicular to the axis of the
associated CO outflow. Its size and mass are estimated to be
0.07 pc $\times$ 0.04 pc
and 2.3 M$_{\odot}$, respectively, from the CH$_{\rm 3}$OH data.
In addition to the elongated envelope,
two compact ($\sim$ 0.03 pc) condensations were found
in the CH$_{\rm 3}$OH line
at the southern edge of the elongated envelope, where
the blueshifted CO outflow emerging from the protostar is located.
In contrast to the elongated envelope,
those compact CH$_{\rm 3}$OH condensations show much larger
line width (up to 2.0 km s$^{\rm -1}$) with centroid velocities
blueshifted by $\sim$ 0.8 km s$^{\rm -1}$.
The compact condensations have momenta ($\sim$ 0.06 M$_{\odot}$
km s$^{\rm -1}$) comparable to that of
the blueshifted molecular outflow. In addition, they are gravitationally
unbound, and most probably will dissipate eventually.
These results suggest that the compact condensations are probably
formed in the course of interaction between the outflow and
the ambient gas surrounding the protostar, and that
such interaction may cause dissipation of a part of the ambient gas.
No drastic, localized enhancement of the CH$_{\rm 3}$OH
abundance is, however, observed toward the compact condensations,
implying that there seems to be no significant shock heating at the
compact condensations in spite of the interaction with the outflow.
This may be because the CO outflow velocity ($
form can be found at www.star.ucl.ac.uk/clusters
This workshop will be a follow-up to
the IAU symposium held in Pucon on "Extragalactic Star Clusters" and the
ESO workshop on "Extragalactic Globular Cluster Systems". It will focus on
massive ($>$ 10$^4$ solar masses) young ($